Method for repairing resistance spot welds in aluminum sheet materials

A method of enlarging an undersized spot weld nugget formed within adjacent portions of two aluminum alloy sheets lying flatly against each other, said sheet portions including outer sheet surfaces, and inner sheet surfaces that include said undersized weld nugget, said weld nugget having a peripheral edge and said aluminum alloy sheets comprising electrically resistive aluminum alloy material around said peripheral edge, said method comprising:

• pressing two welding electrodes in electrical contact against respective outer sheet surfaces, said electrodes being aligned in opposition to each other and overlying opposite sides of the peripheral edge of said weld nugget, said electrodes each having a sheet contacting tip sized and shaped to overlie said electrically resistive material around said peripheral edge of said nugget;
• passing a welding current between said electrode tips through said resistive material to melt aluminum alloy sheet material within said outer surfaces and around the periphery of said undersized nugget;
• and
• stopping said current flow and cooling said melted material to form a supplemental weld nugget around the peripheral edge of said undersized weld nugget.